Skateboards, skates, scooters, and other rolling sports equipment are typically provided with two or more wheels coupled by bearings to the axles of the equipment. The wheels have been made out of a variety of materials to provide desired characteristics, which include resistance to wear, smooth and fast rolling, and a stable connection to the bearings and axles. Another desired characteristic is a light weight for the wheel, which both improves rolling and provides a wheel with less mass, which makes lifting and maneuvering of the equipment easier. Increasing the width and diameter of the wheels improves the rolling characteristic, but at the expense of adding weight. Using a lighter weight material improves rolling but typically the lighter material is softer, resulting in less resistance to wear and a less stable connection to the bearings and axles.
Reducing the weight of the wheels is desirable for a skateboard because it facilitates the board's use in maneuvers or stunts where the board is rotated about its longitudinal, horizontal axis and/or about its central, vertical axis. The wheels are at a distance from both of those axes and thus the wheels provide an inertial moment to which sufficient force must be applied to overcome the moment and rotate the board about the axes. Thus, the lighter the wheels, the easier the rotating stunts can be performed. The moment of the wheels is the product of their weight and the square of the distance from the wheel to the axis, and thus the wheel weight can be of much greater significance than the weight of other components of the skateboard that are closer to the axis.
Past attempts to reduce the weight of the wheels have including simply reducing the size, i.e., the width and diameter of the wheel, but this degrades the rolling characteristics of the wheel. Another approach used a non-polyurethane, thermoplastic, hollow core with a polyurethane riding surface over the core. Some drawbacks of this approach include that the cores can crack or break under load and stress, the cores are heat sensitive, and thus more likely to fail in high or low temperatures, and the cores tend to become more brittle over. Also, the thermoplastic core is unlike the polyurethane riding surfaces in composition, hardness, and rebound properties, making it more difficult to bind the two together and to get good rolling characteristics.